Indeed.
Apparently "It only costs $XX to fill the tank on my Ranger" leads to the perception of the vehicle being fuel efficient. SMH.
I don't really think that's the reason for the small tanks, since by the time the owner gets to the point of filling the tank he's already bought the vehicle (at least I know I wouldn't pay to put gas in a vehicle that wasn't mine yet
)
Pretty sure the real reason is (a) weight and (b) space. Smaller tanks weigh less which means better MPG figures for CAFE compliance. They also take up less space which leaves more room for other stuff under truck. And since 99.9% of buyers will live and use the truck within 20 miles of a gas station anyway, it's not an issue to them. It's only us weird "broverlanders" that worry about silly things like "range."
EDITED TO ADD: It's interesting to see how a manufacturer chooses to equip a vehicle and what that says about the manufacturer's assumptions about their intended customers. Clearly Ford must think that most of the customers for the Ranger are people who live in urban or suburban areas where fuel range is not an issue. By contrast, they offer a 36 gallon tank as an option on the F-150 which means they must think the intended buyer of an F-150 WOULD be concerned about fuel range, i.e. a customer who lives and/or uses the vehicle in areas where gas stations are far apart.
One thing that is nice about large fuel capacities is that it gives you an option to optimize fuel costs. When your gas tank is large, you can bypass the high-cost gas stations and wait until you get into a lower cost area to fill up. For example, if you were going to Death Valley you could fill up in Las Vegas where gas is cheaper than anywhere in California. Drive all you want in CA and still have enough gas in the tank to make it back to a cheaper station in NV. With a smaller tank, you don't have that option - if you're getting to E and you are in Amargosa or Independence CA, you're paying their price whether you want to or not. Now it's true, you don't have to fill your tank - you just have to put enough in to get you to another station. But that's another PITA that takes time out of your trip, too.
For me, at least, I subscribe to the old aviator's philosophy that says "the only time you ever have 'too much fuel' is when you're on fire."